A power semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (insulated gate Field-Effect Transistor) is used as an inverter device that converts a DC current to an AC current and as a power converting apparatus that converts an AC current to a DC current. In such a power semiconductor element, a current flowing from a collector terminal to an emitter terminal in the IGBT or a current flowing from a drain terminal to a source terminal in the MOSFET is controlled by changing the voltage between the gate and emitter terminals (hereinafter, “VGE voltage”) or by changing the voltage between the gate and source terminals (hereinafter, “VGS voltage”), with charging or discharging between the gate and emitter terminals (hereinafter, “between G-E”) or between the gate and source terminals (hereinafter, “between G-S”).
A drive circuit for executing control of the VGE voltage and the VGS voltage in the power semiconductor element described above, which is the drive circuit for the power semiconductor element, generally operates in accordance with a turn-on signal and a turn-off signal, which are pulse signals transmitted from a control circuit. When a turn-on signal is transmitted to the drive circuit, the drive circuit operates such that it electrically charges between G-E of the IGBT or between G-S of the MOSFET, which is a driving object, thereby increasing the VGE voltage or the VGS voltage. Conversely, when a turn-off signal is transmitted to the drive circuit, the drive circuit operates such that it discharges the electric charge between G-E of the IGBT or between G-S of the MOSFET, thereby decreasing the VGE voltage or the VGS voltage.
The drive circuit for the power semiconductor element includes a constant-voltage drive circuit as described in Non Patent Literature 1 listed below. When a turn-on signal is transmitted from a control circuit to a drive circuit, the constant-voltage drive circuit electrically connects between a positive power supply and a gate terminal of an IGBT or a MOSFET via a gate resistance and then charges between G-E or between G-S to increase the VGE voltage or the VGS voltage, thereby turning on the IGBT or the MOSFET. Further, when a turn-off signal is transmitted from the control circuit to the drive circuit, the constant-voltage drive circuit electrically connects between a negative power supply (or ground 0 V) and the gate terminal via a gate resistance and then discharges the electric charge that has built up between G-E or between G-S, S, so as to decrease the VGE voltage or the VGS voltage.
Further, Patent Literature 1 discloses a technique in which a constant-current drive circuit for supplying a constant current to a gate terminal is provided; the VGE voltage between G-E of a power semiconductor element connected to an output terminal of the constant-current drive circuit is compared to a predetermined voltage value. If the VGE voltage increases to more than a set voltage value, the current of the constant-current drive circuit is decreased.
According to the technique disclosed in Patent Literature 1, variations when turning on can be suppressed, and the current can be increased only when it is necessary. Therefore, a low-loss power semiconductor element and power saving of the drive circuit can be realized.